Hotels, office buildings and the like require door locks on a large number of individual rooms. In a hotel, for example, the door lock of each guest room should have a different key for successive guests. Also, at a given time, a guest room door lock must be operable by different keys assigned to hotel personnel, such as the maid, housekeeper and other levels of hotel management. For security purposes, the keys for each lock must be readily changeable.
In the prior art, locking systems for hotels and the like have been developed which utilize electronic code responsive logic circuits for operation of a lock mechanism.
U.S. Pat. No. 3,906,447, issued Sep. 16, 1975 in the name of Crafton discloses a security system for locks and keys wherein the entrance of an area is controlled by an electronic lock mechanism responsive to a digital coded key. A key code is stored in each lock mechanism and is compared with the key code on a digital coded key. If correspondence exists, entrance to the secured area is granted. Imprinted on the key is an order code which corresponds to the time the key is issued. The lock mechanism operates to compare the order code on the key presented to it with the time of presentation, and if the time difference is within a predetermined time interval, the key code on the key is set to the lock mechanism. Furthermore, the time of departure code is imprinted on the key when issued and is entered into the lock mechanism when the order code is presented thereto. When the departure time is reached, the lock mechanism automatically changes at random the stored key code, thus preventing the guests from entering the room. Also included is the provision for a pass key. The room register associated with pass key circuitry at each lock mechanism contains a common arbitrary room number. The grace period is set equal to the length of the work shift and the time of departure is set to correspond to the end of the work shift.
U.S. Pat. No. 4,385,231, issued May 24, 1983 in the name of Mizutani et al discloses a lock system for use with cards. Cards have recorded thereon a secret number, a plurality of subnumbers, a specifying code for selecting at least one of the subnumbers, and an effective period. The lock includes a card reader, a memory for storing a secret number, specifying code and effect period, and a processing unit for unlocking. When the secret number on the card is identical to that in memory, unlocking occurs. If the secret number on the car is not identical with the secret number in the memory, the processor checks whether or not the secret numbers are in predetermined relation established with use of the subnumbers selected by the specifying code in the memory from among the plurality of subnumbers on the card, and gives an unlocking instruction and stores in memory for renewal of the secret number, the effective period and the specifying code on the card.
U.S. Pat. No. 4,644,484, issued Feb. 17, 1987 in the name of Flynn et al discloses an access control system utilizing a clock. A card reader has a crystal controlled time based clock. Entry is granted when the proper information is entered to the card reader through a key. The card reader is operable to provide access control of the secured area according to a schedule operable relative to the card reader clock without external reference signals. A dipwitch is used to compensate for crystal variations. Software adjustment is provided to the time base clock.
A general object of this invention is to provide an improved security device which is especially adapted for use in controlling a door lock mechanism and which overcomes certain disadvantages of the prior art.